| Summary: | Concurrently achieving high energy storage density (ESD) and efficiency has always been a big challenge for electrostatic energy storage capacitors. In this study, we successfully fabricate high-performance energy storage capacitors by using antiferroelectric (AFE) Al-doped Hf<sub>0.25</sub>Zr<sub>0.75</sub>O<sub>2</sub> (HfZrO:Al) dielectrics together with an ultrathin (1 nm) Hf<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2</sub> underlying layer. By optimizing the Al concentration in the AFE layer with the help of accurate controllability of the atomic layer deposition technique, an ultrahigh ESD of 81.4 J cm<sup>−3</sup> and a perfect energy storage efficiency (ESE) of 82.9% are simultaneously achieved for the first time in the case of the Al/(Hf + Zr) ratio of 1/16. Meanwhile, both the ESD and ESE exhibit excellent electric field cycling endurance within 10<sup>9</sup> cycles under 5~5.5 MV cm<sup>−1</sup>, and robust thermal stability up to 200 °C. Thus, the fabricated capacitor is very promising for on-chip energy storage applications due to favorable integratability with the standard complementary metal–oxide–semiconductor (CMOS) process.
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